1. Field of the Invention
The present invention relates to a method for controlling a constant-pressure fluid, and more particularly to a method for controlling a constant-pressure fluid, whereby an inverter with a build-in controller is provided to control rotation speed of a pump.
2. Description of Related Art
In the present day, primary demands of a constant-pressure water supply system are how to maintain a constant-pressure condition, how and when to detect a normal and abnormal operation condition. Hence, a controller is used to adjust an output frequency of an inverter to control rotation speed of a pump according to a variation quantity of water pressure.
Reference is made to FIG. 1 which is a block diagram of a related art constant-pressure water supply system. The constant-pressure water supply system comprises a pump 10A, a pressure gauge 12A, a controller 14A, and an inverter 16A. The pump 10A is used to pump water from an external water source. The pressure gauge 12A is used to measure a water pressure value of a pipe connected to the pump 10A, and the water pressure value is converted into a feedback pressure value. The controller 14A is used to receive the feedback pressure value and the feedback pressure value is operated to adjust an output frequency of the inverter 16A. Therefore, the rotation speed of the pump 10A can be controlled in the constant-pressure condition.
Although many different types of the controllers 14A have been designed, the PID controller is applied generally in industrial automation field, and more particularly to temperature, pressure, and fluid control. The PID controller has some advantages: lower cost, better control performance, less tune parameters, and better anti-interference function.
However, in the related art constant-pressure water supply system, the controller 14A is connected between the pressure gauge 12A and the inverter 16A. Hence, it is difficult to integrate and set up these devices, and the cost of the controller 14A also increases.